Fuel cell system

A fuel cell system, comprising:

• a fuel cell stack;
• a cathode compressor configured to supply a cathode gas;
• a cathode flow passage connected to the fuel cell stack, for the cathode gas to flow;
• a bypass flow passage branching from the cathode flow passage upstream of the fuel cell stack, thereby bypassing the fuel cell stack;
• a bypass valve provided on the bypass flow passage, and configured to adjust a cathode flow rate flowing through the bypass flow passage;
• a stack flow rate sensor configured to detect a cathode flow rate supplied to the fuel cell stack;
• a compressor flow rate sensor configured to detect a cathode flow rate taken into the cathode compressor;
• and
• a controller configured to:
• calculate a flow rate necessary for the fuel cell stack depending on a state of a fuel cell;
• calculate a flow rate which required from the cathode compressor depending on a requirement different from the requirement by the fuel cell stack;
• and
• select a first cathode flow rate control when the flow rate required from the cathode compressor is more than the flow rate required by the fuel cell stack, the first cathode flow rate control being performed so as to control the cathode compressor based on the flow rate required from the cathode compressor and a compressor flow rate detected by the compressor flow rate sensor, and control the bypass valve based on the flow rate required by the fuel cell stack and a stack flow rate detected by the stack flow rate sensor, and
• select a second cathode flow rate control when the flow rate required by the fuel cell stack is more than the flow rate required from the cathode compressor, the second cathode flow rate control being performed so as to control the cathode compressor based on the flow rate required by the fuel cell stack and the stack flow rate detected by the stack flow rate sensor.